The present invention relates to screw couplings in general, and more particularly to improvements in couplings of the type wherein an externally threaded tubular member (hereinafter called nipple for short) cooperates with a nut to clamp and/or otherwise engage an elongated conductor, a cable, a hose, a conduit or an analogous body in order to hold the body against axial movement and/or to prevent leakage of a fluid medium around the confined portion of the body.
It is already known to provide the nipple of a screw coupling with axially parallel flexible prongs or tongues which are flexed inwardly toward the axis of the nipple when the nut is rotated in a direction to be threaded onto the nipple. The inwardly flexed prongs thereby bear against the confined portion of the body or against a sealing element which is interposed between the body and the nipple. Reference may be had, for example, to German Pat. No. 2,132,951 which discloses a nipple adapted to extend through a wall and to surround a conduit and/or an electric cable. The nipple mates with a nut serving to deform a plastic sealing insert which has axially extending straight slots and can be deformed in response to application of the nut so that the insert is held in liquid- and gas-tight sealing engagement with the external surface of the tube or conductor which extends through the nipple. The slots enable the prongs of the insert to overlap each other in fanwise fashion in response to proper threading of the nut onto the nipple.
German Pat. No. 2,631,996 discloses a modified plastic screw coupling wherein the prongs include tooth-shaped portions and can partially overlap each other. The tooth-shaped portions are engaged by helical internal teeth of the nut to prevent undesirable axial displacements of the nut and nipple relative to each other. The internal teeth are intended to move the free end portions of the prongs radially inwardly one after the other whereby the prongs partially overlap each other and the internal teeth of the nut move into engagement with the tooth-shaped portions of the prongs.
A further screw coupling is disclosed in German Utility Model No. 8,415,525 and serves to engage a cable which passes through the nipple. The prongs of the nipple form a ring, and at least one prong is configurated in such a way that it moves radially inwardly in response to application of the nut to thereby establish a non-circular engagement between the annulus of prongs and the confined cable. The one prong has mutually inclined surfaces which cause it to move radially inwardly beyond the neighboring prongs in response to threading of the nut onto the nipple. The prongs deform a sealing element, which surrounds the cable, in such a way that the region of contact between the sealing element and the annulus of prongs has a non-circular outline.